Radio frequency communication network having adaptive communication parameters

ABSTRACT

Improved apparatus for a radio communication network having a multiplicity of mobile transceiver units selectively in communication with a plurality of base transceiver units which communicate with one or two host computers for storage and manipulation of data collected by bar code scanners or other collection means associated with the mobile transceiver units. The radio network is adaptive in that in order to compensate for the wide range of operating conditions a set of variable network parameters are exchanged between transceivers in the network. These parameters define optimized communication on the network under current network conditions. Examples of such parameters include: the length and frequency of the spreading code in direct-sequence spread spectrum communications; the hop frame length, coding, and interleaving in frequency-hopping spread spectrum communications; the method of source encoding used; and the data packet size in a network using data segmentation. The invention is preferably to be applicable as an upgrade of an existing data capture system wherein a large number of hand-held transceiver units operate over an extensive area to gather data in various places, requiring the use of multiple base stations. In a variety of such installations such as warehouse facilities, distribution centers, and retail establishments, it may be advantageous to utilize not only multiple bases capable of communication with a single host, but with multiple hosts as well.

INCORPORATION BY REFERENCE

The following patent applications are incorporated in their entirety byreference:

1. abandoned application of Charles D. Gollnick, et al., U.S. Ser. No.07/857,603 filed Mar. 30, 1992 (Attorney Docket Nos. DN37834XA; 92 P327);

2. pending U.S. patent application of Meier, et al., Ser. No. ______,filed Oct. 30, 1992 (Attorney Docket Nos. DN37882YA; 92 P 758);

3. abandoned application of Ronald L. Mahany, U.S. Ser. No. 07/485,313filed Feb. 26, 1990 (Attorney Docket Nos. DN36500Y; 91P349);

4. pending application of Steven E. Koenck, et al., U.S. Ser. No.07/305,302 filed Jan. 31, 1989 (Attorney Docket Nos. DN36649; 91 P 422);

5. application of Ronald L. Mahany, et al., U.S. Ser. No. 07/389,727filed Aug. 4, 1989 (Attorney Docket Nos. DN36500X; 91P258), now issuedas U.S. Pat. No. 5,070,536 on Dec. 3, 1991;

6. application of Marvin L. Sojka, U.S. Ser. No. 07/292,810 filed Jan.3, 1989 (Attorney Docket Nos. DN36625X; 91P420), now issued as U.S. Pat.No. 4,924,462 on May 8, 1990; and

7. European Published Patent Application EPO 353759 published Feb. 7,1990.

AUTHORIZATION PURSUANT TO 37 C.F.R. 1.71 (d) AND (e)

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserve all copyrightrights whatsoever.

BACKGROUND OF THE INVENTION

The present invention in a preferred implementation relates toimprovements in radio data communication networks wherein a number ofmobile transceiver units are to transmit data to a number of basestations under a wide range of operating conditions. To compensate forthe wide range of operating conditions, adaptability has been providedusing an exchange of parameters that define the nature of the networkcommunication. The invention is preferably to be applicable as anupgrade of an existing data capture system wherein a number of hand-heldtransceiver units of an earlier design are already in the fieldrepresenting a substantial economic investment in comparison to the costof base stations, accessories and components. In installations spreadover an extensive area, a large number of mobile portable transceiverunits may be employed to gather data in various places and multiple basestations may be required. In a variety of such installations such aswarehouse facilities, distribution centers, and retail establishments,it may be advantageous to utilize not only multiple bases capable ofcommunication with a single host, but with multiple hosts as well.

An early RF data collection system is shown in Marvin L. Sojka, U.S.Pat. No. 4,924,462 assigned to the assignee of the present application.This patent illustrates (in the sixth figure) a NORAND® RC2250 NetworkController which supports one base transceiver for communication withmultiple mobile portable transceivers. The exemplary prior art device iscapable of communicating with a host computer through an RS232Cinterface at up to 19,200 baud in asynchronous mode. In order for anoptional RS422 interface to be substituted for an RS232C interface, theunit must be opened and substitute circuitry components installed withinit.

SUMMARY OF THE INVENTION

The present invention provides an improved data communication systemwhich maintains RF communication links between one or more hostcomputers and one or more base transceiver units, each of which may becommunicative with many mobile portable transceiver units being movedabout a warehouse complex for the collection of data. Specifically, theinvention provides a data communication system for collecting andcommunicating data in the form of RF signals which has a plurality of RFtransceivers that store and modify at least one variable operatingparameter. From the stored parameter(s), each of transceivers controlthe operation of transmission and reception. The transceivers alsoevaluate the effect of the stored parameter based by analyzing eachtransmission received, and determine whether to make changes in thestored parameter. If changes are needed, the transceivers, modify andstore the modified operating parameter and begin operation basedthereon.

The operating parameters involve: 1) the size of data segments to betransmitted; 2) the length or frequency of the spreading code used fordirect-sequence spread spectrum communication; 3) the hopping rate,coding, and interleaving for frequency-hopping spread spectrumcommunication; and 4) the type of RF source encoding used.

In addition, the RF transceivers used in the data communication networkof the present invention use system-default values to reset theoperating parameters if a series of failed communication exchangesoccurs, so that communication can be re-established.

It is therefore an object of the invention to provide an adaptive radiocommunication system which permits the interconnection of one or twohost computer devices to a multiplicity of base transceiver units whichmay include both prior art existing installed units and new generationunits capable of spread spectrum radio transmission.

It is a further object of the invention to provide an adaptive RP datacommunication system which optimizes communication based on a set ofoperating parameters.

It is a further object of the invention to provide an adaptive RF datacommunication system which maintains communication based on a set ofoperating parameters for optimizing communication, wherein the operatingparameters involve: 1) the size of data segments to be transmitted; 2)the length or frequency of the spreading code used for direct-sequencespread spectrum communication; 3) the hopping rate, coding, andinterleaving for frequency-hopping spread spectrum communication; and 4)the type of RF source encoding to be used.

It is a further object of the invention to provide a radio communicationsystem network controller which via a communication exchange optimizes aset of operating parameters, yet returns the parameters to theirprevious or system-default values upon failed communication.

These and other objects of the invention will be apparent fromexamination of the detailed description which follows.

DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a block diagram of the prior art data communication system.

FIG. 2 is a perspective view of the invention.

FIG. 3 is a schematic representation of an exemplary radio communicationsystem utilizing the invention.

FIG. 4 is a diagrammatic illustration of the control circuitry elementsof the invention.

FIG. 5 is a rear elevation view of the invention.

FIG. 6 is a diagrammatic illustration of the application specificintegrated circuit of the invention.

FIG. 7 is a block diagram showing an exemplary implementation ofintelligent network and router transceiver units such as the networktransceiver units of FIG. 3.

FIG. 8 is a diagram of an RP system utilizing a network controlleraccording to FIGS. 2-6, with one of its network ports configured forcommunication with a second host, and another of its ports coupled witha multiplicity of RF transceivers via an adapter unit.

FIG. 9 is a diagram illustrating the use of two network controllersaccording to FIGS. 2-6, configured for dual host computers each, andhaving their relatively high data rate extended distance network portscoupled with a multiplicity of intelligent network and routertransceiver units implemented according to FIG. 7.

FIG. 10 is a diagram similar to FIG. 9 but showing the part of couplednetwork controllers interfaced to a common relatively high data ratesystem having multiple hosts (e.g.) a local area network of the Ethernettype or equivalent e.g. fiber optic type.

FIG. 11 is a diagram similar to FIG. 10 but indicating the networkcontrollers being coupled to respective different high data ratemultiple host systems (e.g., token ring type local area networks orother individual networks e.g., fiber optic loop networks of thecollision-sense multiple-access type).

FIG. 12 is a view similar to FIG. 9 but intended to diagrammaticallyindicate a distribution of network and router transceivers and otherelements of an on-line RF data collection system over an extensive areaof a facility e.g. of one of the types previously mentioned.

FIG. 13 shows an intelligent controller and radio base unit whichunifies controller and radio components such as shown in FIG. 7 into asingle housing of the size represented in FIGS. 2 and 5.

FIG. 14 shows a diagrammatic illustration of the signal processing fortwo of four pairs of communication ports of the multiple base adapter ofthe RF data collection system illustrated in FIG. 8.

FIG. 15 is a diagram of parts of an RF data collection system utilizinga network controller according to FIGS. 2-6 and a multiple base adapteraccording to FIG. 14, with eight base transceiver units coupled to themultiple base adapter.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an existing radio frequency data transmission system 10wherein a base station transceiver means 11 has a number of mobiletransceiver units such as 12A, 12B, . . . , 12N in radio communicationtherewith.

By way of example, the base station may be comprised of a radio baseunit 14 such as the model RB3021 of Norand Corporation, Cedar Rapids,Iowa, which forms part of a product family known as the RT3210 system.In this case, the radio base 14 may receive data from the respectivemobile RF terminals, e.g. of type RT3210, and transmit the received datavia a network controller and a communications link 16 (e.g. utilizing anRS-232 format) to a host computer 17.

The data capture terminals 12A, 12B, . . . , 12N may each be providedwith a keyboard such as 18, a display as at 19, and a bar code scanningcapability, e.g., via an instant bar code reader such as shown in U.S.Pat. No. 4,766,300 issued Aug. 23, 1988, and known commercially as the20/20 High Performance Bar Code Reader of Norand Corporation.

FIG. 2 provides a perspective view of the invention 40 in the preferredembodiment case 20. Front panel 22 is provided with display 24 andselect key 26, up key 28 and down key 30. Power indicator 32 comprises alow power green light emitting diode which is energized when power issupplied to the invention 10. Error condition indicator 34 is a yellowLED which is software controlled to be energized if the invention 10 isin error condition.

FIG. 3 discloses a diagrammatic illustration of a radio communicationsystem in accordance with the present invention. Invention networkcontroller 40 is coupled to host computer 42 such that data may beinterchanged between the devices over host communications link 44, whichmay be either in an RS232C format or selectively in an RS422 format. Thehost communication link 44 couples to controller 40 at host port 46.

First communication port 48 of controller 40 provides means for couplingof network 50 to controller 40. Network 50 comprises a number of base RFtransceiver units 52A, 52B and 53B, each of which may be selectivelyemployed in the radio frequency communication of data from mobiletransceiver units. It is to be understood that base transceiver units 52are designed and equipped to be operable in the exchange of data withnetwork controller 40 over network link 56 such that each basetransceiver unit 52A, 52B, or 53C may independently exchange data withnetwork controller 40 through first communication port 48. When firstcommunication port 48 is intended for operation with a network such asnetwork 50 of base transceiver units 52A, 52B and 53C, for example,network controller 40 is selectively operated to provide an RS485interface at first communication port 48. First communication port 48may be alternately selected to operate as an RS232C interface, as anRS422 interface, as a proprietary NORAND® Radio One Node Networkinterface or as a high speed V.35 interface. The selection of interfaceto be provided at first communication port 48 is front panel controlled,that is, the user may operate front panel keys 28, 30 and 26 (See FIG.2) to direct the proper interface to be provided at first communicationport 48.

Base transceiver units 52A, 52B, and 52C are coupled to network link 56by serial means, rather than parallel means, and each may be caused totransmit or to receive independently from the others while additionallybeing communicative with network controller 40 in a randomly chosenfashion.

It is further to be understood that interface translation is providedwithin controller 40 such that data communicated at first communicationport 48 may be directed to host 42 at port 46 via properly choseninterface means as is required by the host 42 with which communicationis intended.

Like first communication port 48, second communication port 57 may beinternally switched among interface choices of these types: RS232C,RS422, V.35, RS485 and proprietary NORAND® Radio One Node Networkinterface. In the illustrated arrangement of FIG. 3, for example, secondcommunication port 57 is coupled over third link 53 to previouslyinstalled base transceiver 54, which heretofore had been used in a priorart system as is illustrated in FIG. 1. Because of limitations of basetransceiver 54, it must communicate via RS232C interface format andtherefore, second communication port 57 must be selected to operate inRS232C interface mode. However, when second communication port 57 isdesired to communicate with a network via RS485 interface, front panelkeys 26, 28 and 30 may be manipulated by the user to provide the RS485interface availability at second communication port 57. Likewise, secondcommunication port 57 may be selected to operate as an RS422 interface,as a V.25 interface, or as the proprietary NORAND® Radio One NodeNetwork interface.

Diagnostic port 55 provides a fourth communication pathway for networkcontroller 40, providing an asynchronous port operable at 300 to 19,200baud as an RS232C interface. When desirable, diagnostic port 55 may becoupled by diagnostic link 58 to diagnostic device 60 for purposes oferror diagnosis of controller 40 by diagnostic device 60, or forreprogramming of memory devices within controller 40 when desired. It iscontemplated that diagnostic device 60 comprises a 16 or 32 bitmicroprocessor commonly known as a personal computer or “PC”. The modeof coupling between diagnostic device 60 and network controller 40 maybe direct or through remote means by use of a modem.

Referring now to FIG. 4, a central processing unit 70 is provided withat least four data communication ports, illustrated at numerals 71, 72,73, and 74. First data communication port 71 may be selectively coupledto RS232 interface member 76 or V.35 interface member 78. The choice ofwhether RS232 interface member 76 or V.35 interface member 78 is chosenis dependent upon the operating characteristics presented by the hostcomputer, such as host computer 42 of FIG. 3, with which networkcontroller 40 will communicate. The choice of whether firstcommunication port 71 is coupled to interface member 76 or to interfacemember 78 depends on the front panel selection made by the user by keys26, 28, and 30 shown in FIG. 2.

Second communication port 72 may be selectively coupled to RS232 member80 or to RS485 interface member 82 or to RS422 interface member 84 or toNORAND® Radio One Node Network proprietary interface member 86. By useof front panel keys 26, 28, and 30 of FIG. 2, the user may select secondcommunication port 72 to be coupled to any one of interface members 80,82, 84, and 86.

Third communication port 73 is identical to second communication port 72in functionality, being selectively couplable to RS232 interface member88, to RS485 interface member 90, to RS422 interface member 92 or toNORAND® Radio One Node Network proprietary interface member 94.

In the preferred embodiment of the invention 40, central processing unit70 of FIG. 4 comprises a Motorola™ 68302 integrated chip cooperativewith an application specific integrated circuit. Central processing unit70 employs novel features allowing the bidirectional use of a datacommunicative line of the Motorola™ 68302 chip and a single clock signalline to eliminate the need for coder-decoder members to be associatedwith the Motorola™ 68302 chip while allowing the use of only one pair ofsignal wires to be coupled to the RS485 interfaces 82 and 90 of FIG. 4.

Fourth communication port 74 of central processing unit is coupled toasynchronous RS232 interface member 97 to be available forinterconnection of a diagnostic device therewith.

Also coupled to central processing unit 70 are display member 24 andkeyboard member 31 with which keys 26, 28, and 30 of front panel 22(FIG. 2) are interactive.

Memory elements including EPROM element 96, DRAM unit 98, FLASH memoryunit 100 and EEPROM element 102 are intercoupled with each other andwith central processing unit 70.

Power supply member 104 is selectively attachable to invention networkcontroller 40. In order to avoid the necessity of different models ofnetwork controller 40 depending on the local electrical power utility'soperating characteristics, power supply 104 is provided in optionalmodels depending on the country in which it is to be used, power supply104 being capable of providing satisfactory output power to networkcontroller 40 regardless of the voltage or frequency of the input sourceprovided to power supply 104.

The application specific integrated circuit (ASIC) used in the inventionnetwork controller 40 is disclosed in FIG. 6 and is identified by the isnumeral 120. ASIC 120 comprises a central processor unit interface 122member which is coupled to the central processor unit bus by CPU buslink 124 which extends from ASIC 120. Also coupled to the CPU bus link124 is dynamic random access memory (DRAM) timing element 126, whichprovides network controller 40 with timing signals for the DRAM member98 illustrated in FIG. 4 when memory refresh of the DRAM 98 isindicated. DRAM timing element 126 is also coupled exteriorly to theASIC 120 to DRAM member 98 by DRAM link 127.

Central processing unit interface 122 is coupled to asynchronous signalprocessing element 128 by signal path 130. Asynchronous signalprocessing element 128 comprises a baud rate generator cooperative witha universal asynchronous receiver-transmitter.

Also coupled to central processing unit interface 122 is network clockand control member 132 which comprises a programmable network clockgenerator which can be selectively programmed to generate an optionalclock speed for a network to be coupled through RS485 interfaces 82 and90 seen in FIG. 4. Network clock and control member 132 also providesdetection means for detections of failure conditions on a linked networkand provides control signals to system components in response thereto,including interrupt signals to programmable interrupt coordinatorcircuitry included in central processing interface 122. Network clockand controller member 132 provides data encoding by the FMO standard,then the encoded data may be operated upon by RS485 interfaces 82 and 84and transmitted and received by single twisted pair means to multipleserially networked base transceiver units exemplified by basetransceiver unit 52A, 52B, and 52C illustrated in FIG. 3.

Keyboard controller element 134 is coupled to central processing unitinterface and provides a link exterior to ASIC 120 to keyboard 31 (SeeFIG. 3).

FLASH memory/EEPROM logic control member 136 is coupled to centralprocessing unit interface 122 and comprises control functions for FLASHmemory element 100 and EEPROM memory element 102 of FIG. 3.

Central processing unit interface 122 is also coupled by line 138 tolatches exterior to ASIC 120.

It is to be understood that the base transceiver units 52A, 52B, and 52Cillustrated in FIG. 3 are communicative with mobile transceiver units byelectromagnetic radio means. The mobile transceiver units may beassociated with bar code scanning devices such as the NORAND® 20/20 HighPerformance Bar Code Reader whereby the scanning devices scan an objecthaving a bar code associated therewith and collect information stored inthe bar code, which information is then transmitted through the mobiletransceiver units to base transceiver units such as base transceiverunits 52A, 52B, and 52C or base transceiver unit 54 of FIG. 3. The barcode data received by said base transceiver units is then transmitted inthe example of FIG. 3, over network 50 by base transceiver units 52A,52B, or 52C, or over link 53 by base transceiver unit 54, to networkcontroller 40 which performs the routing and delivery of the data to thestationary data processor, or processors, such as shown for example, byhost 42 of FIG. 3.

DESCRIPTION OF FIGS. 7 THROUGH 11

FIG. 7 shows a block diagram of a particularly preferred intelligentbase transceiver unit known as the RB4000. It will be observed that thecomponents correspond with components of the network controller of FIG.4, and similar reference numerals (preceded by 7-) have been applied inFIG. 7. Thus, the significance of components 7-70 through 7-73, 7-76,7-82, 7-96, 7-98, 7-100 and 7-104 will be apparent from the precedingdescription with respect to FIGS. 4 and 6, for example. I/O bus 700 maybe coupled with a spread spectrum transmission (SST) or ultra highfrequency (UHF) transceiver 701 which may correspond is with any of thetransceivers of units 52A, 52B, 52C or 54 previously referred to. Thenetwork controller 70 could have a similar RF transceiver coupled withits data port 72 or 73 and controlled via input/output bus 400, e.g. fordirect RF coupling with router transceivers such as 901, 901, FIG. 9.

Referring to FIG. 8, a network controller 40 is shown with port 71configured for interface with a host port type SNA V. 35 56K/64K bitsper second.

Port 72 is shown as configured for communication with a personalcomputer of the PS/2 type operating asynchronously at 38.4K bits persecond. Port 74 is coupled with a modem 8-60 providing for remotediagnostics and reprogramming of the network controller 40.

Port 73 of network controller 40 is shown as being connected with anadapter component 801 known as the MBA3000. A specification for theMBA3000 if found in Appendix A following this detailed description. Inthe operating mode indicated in FIG. 8, the adapter 801 serves to couplecontroller 40 sequentially with four radio base transceiver units suchas indicated at 811 through 814. Component 811 is a commerciallyavailable radio base known as the RB3021 which utilizes features ofSojka U.S. Pat. No. 4,924,462 and of Mahany U.S. Pat. No. 4,910,794 bothassigned to the present assignee, and the disclosures of which arehereby incorporated herein by reference in their entirety. Base station811 may communicate with a multiplicity of hand-held RF data terminalssuch as indicated at 821. Details concerning base transceiver units 812and 813, 814 are found in the attached Appendices B and C, respectively.Base 814 is indicated as being coupled with the adaptor 801 via RFbroadband modems 831 and 832. Base units 813 and 814 may communicatewith a variety of mobile transceiver units such as those indicated at833 and 834 which are particularly described in Appendices D and E.

FIG. 9 shows two network controllers 40A and 40B each with its hostports configured as with the controller 40 of FIG. 8. In this example,the second ports 72 of the controllers 40A and 40B are configured forcommunication a relatively high data rate relatively along a distancenetwork channel 56 which may have the characteristics of the serialchannel 56 of FIG. 3, for example, an RS485 channel operating at 384kilobits per second (384K bps). Network base transceivers 52A, 52B and52C may correspond with the correspondingly numbered transceiver unitsof FIG. 3, for example, and the network may have additional networktransceivers such as 52D. Furthermore, the network transceivers may haveRF coupling with router transceiver units such as indicated at 901, 902and 903. Router transceiver unit 902 is illustrated as a RB4000intelligent transceiver such as represented in FIG. 7 and having itsinput/output bus 700 coupled with a peripheral.

FIG. 10 is entirely similar to FIG. 9, for example, except that ports 72of the controllers 40A and 40B are coupled with separate serial typehigh data rate network channels, and ports 73 of the respective networkcontrollers are coupled to a very high speed network e.g. in the severalmegabits per second range such as an Ethernet local area network 1000.Suitable interfaces are indicated at 1001 and 1002.

FIG. 11 is entirely similar to FIG. 9 except that the ports 73 of thenetwork controllers 40A and 40B are coupled with respective local arearing type networks which may be separate from each other and each havetwo or more hosts such as represented in FIG. 9 associated with therespective ring networks such as token rings 1100A and 1100B. Suitableinterface means are indicated at 1101 and 1102.

DESCRIPTION OF FIG. 12

FIG. 12 shows, for example, two network controllers 40A and 40B, eachwith two host computer units such as 42-1A. Host 42-2A is shown with aprinter or other peripheral P1 which may generate bar codes, forexample, for replacement of damaged bar codes or the like. Anotherprinter P2 is shown associated with base 52C, again for example, forproducing bar code labels where those are needed in the vicinity of abase station. In a large warehouse, relatively large distances may beinvolved for a worker to return to a printer such as P1 to obtain a newbar code label. Thus, it may be very advantageous to provide a printerP2 at the base station 52C which may be relatively close to a processinglocation which requires printed labels, e.g. a processing location inthe vicinity of hand-held terminal 12-2 in FIG. 12. A base 52F may havea peripheral P3 associated therewith such as a large screen display, aprinter or the like which may supplement the capabilities of a hand-heldterminal, for example printing out new bar code labels at a convenientlocation, or providing a full screen display, rather than the morelimited screen display area of the hand-held terminal 12-2.

If, for example, a base radio 52D which might be located at the ceilinglevel of a warehouse became inoperative at a time when qualified repairpersonnel were not immediately available, with the present system itwould be feasible to provide a substitute base radio or base radios, forexample, as indicated at 52D1 located at table level or the like.

With the present system, the base radio stations do not necessarilyforward data communications received from a given terminal to aparticular host. For example, hand-held terminal 12-2 may request a pathto printer P2, and such a path may be created via base stations 52D1 and52C. Station 52C upon receipt of the message form terminal 12-2 wouldnot transmit the message to a host but would, for example, produce thedesired bar code label by means of printer P2. Further, terminal 12-2may have provision for digitizing a voice message which might, forexample, be addressed to terminal 12-1. The system as illustrated wouldbe operable to automatically establish a suitable path for example, viastations 52D1, 52C, 52B, 52E and 12-1 for the transmission of this voicemessage in digital form. Successive segments of such a voice messagewould be stored, for example, by the terminal 12-1, and when thecomplete message was assembled, the segments would be synthesized into acontinuous voice message for the user of terminal 12-1 e.g. by means ofa speaker 1201 also useful for sending tone signals indicating valid barcode read, etc.

In accordance with the present invention, a hardware system such asillustrated in FIG. 12 may be physically laid out and then upon suitablecommand to one of the network controllers such as 42-2B, the entiresystem would be progressively automatically self-configured forefficient operation. For example, controller 40B could successively tryits communications options with its output ports such as 71-73,determining for example, that host processors were coupled with ports 71and 72, one operating on a 38.4 kilobit per second asynchronous basisand the other presenting a SNA port for the V.35 protocol at 64 kilobitsper second. For example, on host, 42-1B might be a main frame computer,while the other host 42-2B might be a PS/2 type computer system. Thecontroller 40B having thus automatically configured itself so as to becompatible with the devices connected to ports 71 and 72, could proceedto transmit via port 73 a suitable inquiry message to the networkchannel 56. Although a polling protocol is preferred, each of the basestations could operate, for example, on a carrier-sense multiple-access(CSMA) basis or using a busy tone protocol to respond to the inquirymessage from the controller 40B, until each of the successive bases onthe network had responded and identified itself. Each base, for example,would have a respective unique address identification which it couldtransmit in response to the inquiry message so as to establish itspresence on the network.

The controller 40B could then transmit auto configure commands to thesuccessive bases in turn, instructing the bases to determine whatperipherals and router bases such as 52D1, 52E and 52F were within therange of such base, and to report back to the controller. For example,bases such as 52C and 52F could determine the nature of peripherals P2and P3 associated therewith so as to be able to respond to an inquiryform a terminal such as 12-2 to advise the terminal that a bar codeprinter, for example, was within direct RF range.

In the case of a breakdown of a component of the system such as 52D, itwould merely be necessary to place a router device such as 52D1 at aconvenient location and activate the unit, whereupon the unit could sendout its own broadcast inquiry which, for example, could be answered bythe base stations 52C and 52F, station 52C in turn, advising a relevanthost or hosts of the activation of a substitute router station. Thus,the system is conveniently re-self-configured without the necessity fora technician familiar with the particular configuration procedure. Asanother example, where the base stations are operating utilizing spreadspectrum transmission, the introduction of barriers (such as a new stackof inventory goods) to such transmission between a given base such as52A and various terminals, could result in the base 52A contactingrouter 52E, for example, with a request to become active with respect tothe blocked terminals.

A more detailed example of auto-configuration of the network can befound in pending U.S. patent application of Meier, et al., Ser. No.______, (Attorney Docket Nos. DN37882YA; 92 P 758) filed Oct. 30, 1992,which is incorporated herein by reference.

DESCRIPTION OF FIG. 13

FIG. 13 shows an intelligent integrated controller and radio base unit1300 which is integrated into a single housing or case 1301corresponding to the case or housing 20 of FIG. 2. the housing 1301 maybe provided with an external antenna as diagrammatically indicated at1302 with suitable RF coupling to the radio circuitry indicated at 1303.Components 13-70 through 13-74, 13-76, 13-78, 13-96, 13-97, 13-98,13-100, and 13-102 may correspond with the correspondingly numberedcomponents described with reference to FIG. 4.

SUPPLEMENTARY DISCUSSION

In accordance with the present disclosure, a network controller, orintegrated network controller and radio unit is coupled to one or morehost computers via a standard interface such as commonly encountered inpractice (e.g. RS232, V. 35, Ethernet, token ring, FDDI, and so on). Inthis way, no specialized interface or adapter is required for the host.

Since the preferred network controller can connect to two hosts, if onehost is detected to have failed, or in the event of a system crash, lossof communication link, or the like, the network controller canautomatically switch to the second host. The second host may be a trulyredundant system, or may be a simpler computer of the PC type (aso-called personal computer) that can simply store transactions untilthe main host is restored. As another example, a single host may have asecond port coupled to a second port of the controller especially if acommunication link failure may be a problem. For example, two ports ofthe network controller may be coupled by separate modems with separatephone lines, leading to separate ports of a single mainframe computer,for example an IBM3090. In a fully redundant system, two ports of anetwork controller may be connected respectively to two mainframecomputers such as the IBM3090.

The disclosed network controller can also connect one radio network totwo hosts using RS232 or V.35 ports or to many hosts using a local areanetwork such as Ethernet, token ring, or FDDI. A number of the disclosednetwork controllers (for example, up to thirty-two) can be connectedtogether to interface many hosts to a single radio network. Thehand-held portable terminals in such a network can then talk to any ofthe hosts they choose.

For example where one port of the disclosed network controller iscoupled via its RS232 interface to a mainframe computer such as theIBM3090, another of its ports may be coupled via an FDDI network with asuper computer e.g. the Cray X-MP. Then mobile and/or portable terminalscan access either the main frame or the super computer, or in general,any of the hosts that are connected to the network controller.

As indicated in FIG. 9, four hosts can be on one network. Referring toFIGS. 10 and 11, a multiplicity of hosts may be coupled with each localarea network so as to be in communication with one or more of thedisclosed network controllers. Furthermore, a single disclosed networkcontroller can control two radio networks such as the one indicated at50 in FIG. 3. Where each network such as 50 is limited to thirty-twodevices, the number of devices is doubled with the use of two radionetworks. Two such radio networks may also be utilized for the sake ofredundancy, with a provision for automatic switch-over from one radionetwork to the second if a problem develops on the first. Two radionetworks may also facilitate the use of different radio technologies inone installation.

The various multi-drop local area networks referred to herein, forexample at 7-82 in FIG. 7 and as represented at 56, 56A, 56B, FIGS. 9through 12, and at 13-82 in FIG. 13 may comprise HDLC based local areanetworks operating at up to 2.5 megabits per second and using biphasespace encoding (FMO) for clock recovery from data.

The components 86 and 94, FIG. 4, and component 13-11, FIG. 13, providesa low-cost base radio interface using three pairs of twisted conductors.One pair provides a bidirectional RS485 data line. Another pair is usedfor the clock and has an RS422 electrical configuration, and is onedirectional from the radio to the controller. The third twisted pair isalso RS422 and is used to communicate from the controller to the radiotransceiver to effect mode selection.

Since it is advantageous to operate the network and router RFtransceiver units so as to be compatible with existing mobile datacollection terminals such as shown in Appendix D1 et seq., a preferredmode of operation is based on the RTC protocol as disclosed in theaforementioned incorporated Mahany and Sojka patents and the followingapplications:

(1) U.S. Ser. No. 07/389,727 filed Aug. 4, 1989 (Attorney Docket Nos.36500X; 91 P 258), now issued as U.S. Pat. No. 5,070,536 on Dec. 3,1991.

(2) European Published Patent Application EPO 353759 published Feb. 7,1990.

(3) U.S. Ser. No. 07/485,313 filed Feb. 26, 1990 (Attorney Docket Nos.36500Y; 91 P 349).

The disclosures of applications (1), (2) and (3) are hereby incorporatedherein by reference in their entirety.

An aspect of the invention resides in the provision of a networkcontroller having port means selectively configurable for coupling infirst mode with network RF transceiver units at a relatively high datarate such as 100 kilobits per second or higher, and for coupling in asecond mode with network transceiver units at a relatively low data ratesuch as about twenty kilobits per second. Preferably a single port meanssuch as 2, 3, or 5, 6, FIG. 5, can be software configured to interfaceselectively in the first mode or in the second mode. It is presentlyless expensive to use multiple connectors per port rather than a single37-pin connector for example.

Where a network controller such as 40 operates two high data ratenetworks, for example, one network of RF base transceivers could operatewith the RTC protocol, and the second network could operate according toa different protocol such as that disclosed in pending application Ser.No. 07/660,618 filed on or about Feb. 25, 1991 (Attorney Docket No.37734), in its entirety. It will be apparent that many modifications andvariations may be effected without departing from the scope of theteachings and concept of the present disclosure.

DESCRIPTION OF FIGS. 14 AND 15

FIG. 14 is a block diagram of the circuitry for one pair ofcommunication ports 1401 and 1403 of adapter 801 (FIG. 8) for use incoupling to base transceiver units. Three additional pairs ofcommunication parts for coupling to six additional base transceiverunits are provided in the preferred embodiment of adapter 801 asexemplified by the MBA3000 Multiple Base Adapter further described inAppendix A. It is to be understood that the circuit components coupledto each additional pair of communication ports of adapter 801 isidentical to that shown for first port pair 1A/1A, that is ports 1401and 1403 of FIG. 14. The adapter 801 provides means for connecting thecontroller 40 (FIG. 8) at its port 73 to a multiplicity of radio baseunits illustrated in FIG. 8 as, for example, 811, 812, 813, 814,including in selected pairs. In the preferred embodiment of adapter 801,up to eight radio base units may be coupled through use of adapter 801to a network controller 40, to be controlled by controller 40 inselected pairs thereof. The controller 40 may control the radio baseunits such as 811, 812, 813, 814, (FIG. 8) in simulcast mode, that is,with all base radios interrogating mobile transceiver units such as 821,833, and 834 of FIG. 8 simultaneously, or with the base units beingemployed in pairs to interrogate the mobile transceiver units.

Referring again to FIG. 14, the network controller 40 provides transmitdata and baud rate select signals to adapter 801. Within adapter 801,the controller outputs are converted to TTL levels by TTL converter 1402and they are then provided to buffer 1404 which provides the signals topaired RS232 transceivers 1406 and 1408, and to paired RS422transceivers 1410 and 1412 which deliver the converted signals to ports1401 and 1403 respectively. By this means, the controller's outputsignals are provided to a pair of output ports 1401 and 1403 in bothRS232 and RS422 interface at the same time. An additional threeoutput-port-pairs are provided which may be denominated 2A/2B, 3A/3B and4A/4B, which ports are controlled and operated identically to ports1A/1B identified in FIG. 14 as ports 1401 and 1402. The RS232transceivers 1406 and 1408 and RS422 transceivers 1410 and 1412 andports 1401 and 1403 are illustrative of all circuitry coupled to portpairs of adapter 801.

Similarly, signals provided to adapter 801 by base radios coupled to theoutput port pairs, e.g. ports 1401 and 1403 of FIG. 14, are firstconverted to TTL levels by the RS232 transceivers 1406 and 1408 or bythe RS422 transceivers 1410 and 1412, depending upon which interface ispresented by a pair of base radios at port 1401 and 1403. The signalsprovided to adapter 801 are then forwarded by the transceivers 1406 and1408 or 1410 and 1412 at TTL levels to controller 40. A selection unit1414 provides a push-to-talk selection signal to the RS232 transceivers1406 and 1408 and to the RS422 transceivers 1410 and 1412 to provide PTTselection signals at ports 1401 and 1403 in both RS232 and RS422 format.It is to be understood that similar selection units are associated withremaining port pairs 2A/2B, 3A/3B. 4A/4B so that the ports may beindependently operated.

The adapter 801 of FIG. 8 is exemplified by the MBA3000 multiple baseadapter unit manufactured by the NORAND Corporation of Cedar Rapids,Iowa as shown in Appendix A. Because of the operation of the MBA3000multiple base adapter by dual methods in either RS232 or RS422 signalenvironments, the MBA3000 may be incorporated into systems havingexisting installed base radios which present only an RS232 interface orit may be incorporated into systems having base radios some of whichoperate at RS422 and some at RS232.

FIG. 15 illustrates a preferred arrangement of controller 40 and adapter801 when used in an environment with multiple base radios in multiplewarehouse environments. Controller 40 is coupled to adapter 801 which iscoupled to paired bases 1511, 1512; 1513, 1514; 1515, 1516; and 1517,1518; which are located in warehouses 1501, 1502, 1503 and 1504. Bygeographical separation in warehouse 1501, for example, base radios 1511and 1513 provide substantial coverage of warehouse 1501 such that amobile transceiver being used within warehouse 1501 would becommunicated with by either base radio 1511 or 1513. By the use ofadapter 801, controller 40 may cause interrogation simultaneously bybase radios 1511, 1512, 1513, 1514, 1515, 1516, 1517, 1718, or it maycause sequential interrogation by radio pairs 1511/1512, 1513/1514,1515/1516, or 1517/1518 in succession. When a mobile transceiverresponds by RF communication means with a base radio, e.g. base radio1511, the response is transmitted by base radio 1511 through coupling1521 to adapter 801 which automatically converts the incoming responseto RS232 interface as necessary, to make it suitable for reception bycontroller 40.

Through a system as exemplified in FIG. 15, data collection from anumber of roving mobile transceivers may be initiated by a networkcontroller 40 through a four-warehouse environment. When basetransceiver units 1511 and 1512 have been unsuccessful in establishingcommunication with the desired mobile transceiver unit, controller 40will then cause bases 1513 and 1514 to attempt communication and ifbases 1513 and 1514 are unsuccessful, controller 40 will proceed throughthe other base radio pairs, namely 1515/1516 and 1517/1518, as needed,to establish communication with the desired mobile transceiver unit.Details regarding base transceiver units 1511, 1512, 1513, and 1514 arefound in Appendix B. Details regarding base transceiver units 1515,1516, 1517, and 1518 are found in Appendix D.

The adapter 801 is provided to operate in either simulcast or sequentialmode. In the normal or simulcast mode, adapter 801 allows the use of oneto eight bases, where the bases are configured as four pairs of twobases. In this mode the adapter 801 simulcasts to a single base pair ata time and the four sets of base pairs are selected using a dynamictime-division multiplexing method. The user can configure the adapter801 to use any of the eight base ports, using simulcasting ortime-division multiplexing to best advantage.

There are two sets of base transceiver units, referred to as set A(identified as 1A, 2A, 3A, and 4A) and set B (identified as 1B, 2B, 3B,and 4B). Within a set, the base transceiver units are selected bytime-division multiplexing.

It can be seen in FIG. 15, that there are four pairs of base transceiverunits defined as pairs 1A/1B, 2A/2B, 3A/3B, 4A/4B. Each base transceiverunit of a base pair is simulcasted to at the same time.

The hardware of the adapter 801 allows the selection of the base pairs(pair 1A/1B through 4A/4B) using control lines from the controller 40.Adapter 801 transmits to both base transceiver units of a base pair atthe same time and receives independently from each base simultaneously.

The use of adapter 801 allows an extension of the number of basetransceiver units that can be used in a facility to allow for adequatecoverage, it is important to understand how the base transceiver unitsoperate when simulcasting is used, and when time-division multiplexingis used.

The adapter 801 distributes signals transmitted by controller 40 to basetransceiver pairs at the same time, so if there is an overlap in thecoverage for the two base transceiver units, there may be someinterference. The amount of interference depends on the relative signalstrengths; if the strength is similar in one spot the chance ofinterference is larger that if the signal strengths are different. Thistype of interference could be avoided in some configurations bysplitting coverage areas of pairs of base transceiver units. Anothermethod of covering the overlap area is to place another base (not one ofthe base pairs) to cover the overlap area. The radio signals from themobile transceiver unit may be picked up fully or partially by either orboth base transceiver units of a given pair. However the adapter 801first tries to receive from one base transceiver unit, for example base1511, and if unsuccessful, it then switches to try to receive from asecond base transceiver unit, for example base transceiver unit 1513. Ifthe information is successfully received from the first base transceiverunit, the information from the second base transceiver unit is ignored.Thus the controller assures data does not get sent to the host dataprocessor in duplicate.

The user may couple from one to eight base transceiver units to theadapter 801 and can then configure those base transceiver units asrequired to meet the installation's needs. Any combination of ports ofthe adapter 801 can be used. Thus the user can take advantage of theability to simulcast or sequentially (via time-division multiplexing)access the base transceiver units 1511, 1512, 1513, 1514, 1515, 1516,1517, and 1518.

The following Appendix E provides an exemplary computer program listingfor preferred control instruction for the system disclosed herein.

MULTIPATH FADING AND DATA PACKET SIZE PARAMETERS

In a preferred embodiment, the data (or messages) to be sent through theRF communication link is segmented into a plurality of DATA packets andis then transmitted. Upon receipt, the DATA packets are reassembled foruse or storage. Data segmentation on the RP link provides bettercommunication channel efficiency by reducing the amount of data loss inthe network. For example, because collisions between transmissions on anRF link cannot be completely avoided, sending the data in small segmentsresults in an overall decrease in data loss in the network, i.e., onlythe small segments which collide have to be re-sent.

Similarly, choosing smaller data packets for transmission also reducesthe amount of data loss by reducing the inherent effects ofperturbations and fluctuations found in RF communication links. Inparticular, RF signals are inherently subject to what is termed“multi-path fading”. A signal received by a receiver is a composite ofall signals that have reached that receiver by taking all availablepaths from the transmitter. The received signal is therefore oftenreferred to as a “composite signal” which has a power envelope equal tothe vector sum of the individual components of the multi-path signalsreceived. If the signals making up the composite signal are ofamplitudes that add “out of phase”, the desired data signal decreases inamplitude. If the signal amplitudes are approximately equal, aneffective null (no detectable signal at the receiver) results. Thiscondition is termed “fading”.

An data communication system using segmentation can be found in apending application of Steven E. Koenck, et al., U.S. Ser. No.07/305,302 filed Jan. 31, 1989 (Attorney Docket Nos. DN36649; 91 P 422),which is incorporated herein by reference in its entirety. Specificreference is made to Appendix A thereof.

Normally changes in the propagation environment occur relatively slowly,i.e., over periods of time ranging from several tenths ({fraction(1/10)}'s) of seconds to several seconds. However, in a mobile RFenvironment, receivers (or the corresponding transmitters) often travelover some distance in the course of receiving a message. Because thesignal energy at each receiver is determined by the paths that thesignal components take to reach that receiver, the relative motionbetween the receiver and the transmitter causes the receiver toexperience rapid fluctuations in signal energy. Such rapid fluctuationscan result in the loss of data if the amplitude of the received signalfalls below the sensitivity of the receiver.

Over small distances, the signal components that determine the compositesignal are well correlated, i.e., there is a small probability that asignificant change in the signal power envelope will occur over thedistance. If a transmission of a data packet can be initiated andcompleted before the relative movement between the receiver andtransmitter exceeds the “small distance”, data loss to fading isunlikely to occur. The maximum “small distance” wherein a high degree ofcorrelation exists is referred to hereafter as the “correlationdistance”.

As expressed in wavelengths of the carrier frequency, the correlationdistance is one half (½) of the wavelength, while a more conservativevalue is one quarter (¼) of the wavelength. Taking this correlationdistance into consideration, the size of the data packet forsegmentation purposes can be calculated. For example, at 915 MHz (apreferred RF transmission frequency), a quarter wavelength is about 8.2centimeters. A mobile radio moving at ten (10) miles per hour, or 447centimeters per second, travels the quarter wavelength in about 18.3milliseconds. In such an environment, as long as the segment packet sizeremains well under 18.3 milliseconds, significant signal fluctuationsduring the duration of a packet transmission is unlikely. In such anpreferred embodiment, five (5) millisecond data packet segments arechosen which provides a quasi-static multipath communicationenvironment.

The faster the relative movement between a transmitter and a receiverthe greater the effect of fading, and, therefore, the smaller the datasegment should be. Similarly, if the relative movement is slower, thedata segment can be larger.

Slower fading effects which might be experienced between stationarytransceivers in an office building due to the movement of people, mailcarts, and the like. In a typical application of the present invention,the RP transceiver of a mobile unit may be secured with a bar-codescanner such as a deflected laser beam bar-code scanner or an instantCCD bar-code scanner. In such an example, the bar code data could betransmitted to the base station as the RF transceiver and a scannerdevice were being jointly transported by a vehicle (e.g. a forklifttruck) to another site, or the RF transceiver and a scanner, e.g. as aunitary hand-held device, could be carried by the operator to anothersite as the bar code data was being transmitted to the base station. Insuch situations, fading is more pronounced.

If fading does not pose a problem on a given network, the overheadassociated with segmentation, hand-shaking and reconstruction may not bejustifiable. However, where fading exists, such overhead may berequired.

In many communication environments, the degree of fading effects variesdramatically both from time to time and from installation toinstallation. In the preferred embodiment, transmitters and receiverscommunicate using an optimal data segment size parameter by adapting thesize to conform to the communication environment of the network at anygiven time. For example, if a receiver detects repeated faultytransmissions, the data segment size parameter might be incrementallyreduced (under the assumption that fading caused the faults) until thedata throughput reaches an optimal level. Similarly, the size of thedata segment can be reduced based on a measured indication of the degreeof fading in the network.

One example of a receiver making such a measurement of fading can befound in the abandoned patent application of Ronald L. Mahany, U.S. Ser.No. 07/485,313, filed Feb. 26, 1990, which is incorporated herein byreference. Specifically, in that reference, a received signal strengthindicator (RSSI) circuit is found in the receiver. The RSSI circuitsamples the signal strength of a transmission. If the signal strengthsamples are evaluated in sequence and the trend analyzed, the degree offading can be measured. If the signal strength samples decrease invalue, it is likely that fading is present in the network. However, justbecause fading exists does not require segmentation only if fadingcauses the signal strength to drop below the level of the receiver'ssensitivity is segmentation required.

A fixed threshold value that is located a safe margain above thereceiver's sensitivity is used to determine whether to change the datasegment size. If a trend in signal strength shows values falling belowthe threshold, the data segment size is decreased. If the thresholdlevel is never reached, the segment size might be increased. Inaddition, the trend associated with a group of signal strength samplescan be used to predict the optimal data packet size—the intersection ofthe signal strength samples with the threshold defines a segment lengththat, with a safe margain, can be used effectively used with the currentdegree of fading.

After receiving a data segment, the receiver sends to the transmitterindications regarding: 1) whether the data segment was received withoutfault; and 2) what the new optimal segment size should be. Thetransmitter responds by adjusting the data segment size and then sendingthe next segment. As can be appreciated, the data segments are adaptedbased on the previous transmission. Instead of adjusting on the basis ofthe reception of a single data segment (the previous transmission),other techniques for adjustment are contemplated. For example, thetransmitter may also utilize a threshold window (or weighted averaging),inside of which the segment size will not be changed. Only if therequested change by the receiver falls outside of the threshold windowwill the segment size change. Similarly, the receiver might also utilizesuch a window—only requesting a change when the newly forecasted,optimal segment size falls outside of the window.

DIRECT-SEQUENCE SPREAD SPECTRUM PARAMETERS

As described above, the network controller provides an interface to boththe older generation UHF radio transceivers and newer generation spreadspectrum transceivers. A spread spectrum broadcasting system uses asequential pseudo-noise signal to spread a signal that is in arelatively narrow band over a wider range of frequencies. It is thesubject of standards issued by the Federal Communications Commission(FCC) that provide usable spectrum at low power levels for communicationin limited areas such as warehouses, office buildings, and the like. Theuse of spread-spectrum techniques minimizes interference with othersusing the same channels in the spectrum.

A transmitter using direct-sequence spread spectrum transmission uses aspreading-code of a higher frequency than that of the data rate toencode the data to be sent. This higher frequency is achieved byincreasing the chip clock rate (wherein each chip constitutes an elementof the spreading-code). Using the same spreading code, the receiverdecodes the received signal while ignoring minor faults which occurredin transmission, providing noise immunity and multipath signalrejection. The frequency and length of the spreading-code can be variedto offer more or less multipath signal rejection or noise immunity.Although it may result in improved communication, increasing thefrequency or length of the spreading-code requires additional overheadwhich may not be justifiable unless necessary.

FREQUENCE-HOPPING SPREAD SPECTRUM PARAMETERS

Frequency-hopping is the switching of transmission frequencies accordingto a sequence that is fixed or pseudo-random and that is available toboth the transmitter and receiver. Adaptation to the communicationenvironment via an exchange in frequency-hopping operating parameters ispossible, for example, via selective control of the hopping rate orthrough the use of coding or interleaving. The greater the degree offrequency selectivity of the fading envelope (i.e., when fading issignificant only over a portion of the spectrum of hopping frequencies),the greater the benefit of such adaptation.

Particularly, a parameter indicating the hopping rate can be varied tominimize the probability that the channel characteristics willdetrimentally change during the course of a communication exchange. Tovary the hopping rate is to vary the length of a hopping frame. Althoughmultiple data (or message) exchanges per hopping frame is contemplated,the preferred hopping frame consists of a single exchange of data. Forexample, in a polling environment, the hopping frame might consistof: 1) a base station transmitting a polling packet to a roamingterminal; 2) the roaming terminal transmitting data in response; and 3)the base station responding in turn by transmitting an acknowledgepacket. Each hopping frame exchange occurs at a differentpseudo-randomly chosen frequency.

For optimization, the hop frame length is adjusted to be as long aspossible, while remaining shorter than the coherence time of the channelby some safety margin. Although such adjustment does not eliminate theeffects of fading, it increases the probability that the characteristicsof the channel will remain consistent during each hopping frame. Thus,in the preferred embodiment, if the polling packet transmission issuccessfully received, the probability of successful receipt of the data(or message) and acknowledge is high.

Another parameter for changing frequency-hopping performance is that ofcoding. Coding on the channel for error correction purposes can beselectively used whenever the probability of data or message loss due tofading is high. In particular, coding methods which provide burst errorcorrection, e.g., Reed-Solomon coding, can be applied if the hop lengthis likely to exceed the coherence time of the channel. Such codingmethods allow some portion of the data to be lost and reconstructed atthe expense of a 30-50% reduction in throughput. The operating parameterfor coding indicates whether coding should be used and, if so, the typeof coding to be used.

An operating parameter indicating whether interleaving should be usedalso helps to optimize the communication channel. Interleaving involvesbreaking down the data into segments which are redundantly transmittedin different hopping frames. For example, in a three segment exchange,the first and second segments are sequentially combined and sent duringa first hopping frame. In a subsequent hopping frame, the second andthird segments are combined and sent. Finally, the third and firstsegments are sequentially combined and transmitted in a third hoppingframe. The receiving transceiver compares each segment received with theredundantly received segment to verify that the transmission wassuccessful. If errors are detected, further transmissions must be madeuntil verification is achieved. Once achieved, the transceiverreconstructs the data from the segments.

Other methods of interleaving are also contemplated. For example, asimpler form of interleaving would be to sequentially send the datatwice without segmentation on two different frequencies (i.e., on twosuccessive hops).

As can be appreciated, interleaving provides for a redundancy check butat the expense of data or message throughput. The interleaving parameterdetermines whether interleaving is to be used and, if so, the specificmethod of interleaving.

In addition, any combination of the above frequency-hopping parametersmight interact to define an overall operating configuration, differentfrom what might be expected from the sum of the individual operatingparameters. For example, selecting interleaving and coding, throughtheir respective parameters, might result in a more complexcommunication scheme which combines segmentation and error correction insome alternate fashion.

SOURCE ENCODING PARAMETERS (FOR NARROWBAND APPLICATION)

In the United States, data communication equipment operating in theultra-high frequency (UHF) range under conditions of frequencymodulation (FM) is subject to the following limitations.

(1) The occupied band width is sixteen kilohertz maximum with fivekilohertz maximum frequency deviation.

(2) The channel spacing is 25 kilohertz. This requires the use of highlyselected filtering in the receiver to reduce the potential forinterference from nearby radio equipment operating on adjacent channels.

(3) The maximum output power is generally in the range of ten to threehundred watts. For localized operation in a fixed location, however,transmitter power output may be limited to two watts maximum, andlimitations may be placed on antenna height as well. These restrictionsare intended to limit system range so as to allow efficient re-use offrequencies.

For non-return to zero (NRZ) data modulation, the highest modulatingfrequency is equal to one half the data rate in baud. Maximum deviationof five kilohertz may be utilized for a highest modulation frequencywhich is less than three kilohertz, but lower deviations are generallyrequired for higher modulation frequencies. Thus, at a data rate of tenthousand baud, and an occupied bandwidth of sixteen kilohertz, the peakFM deviation which can be utilized for NRZ data may be three kilohertzor less.

Considerations of cost versus performance tradeoffs are the major reasonfor the selection of the frequency modulation approach used in thesystem. The approach utilizes shaped non-return-to-zero (NRZ) data forbandwidth efficiency and non-coherent demodulation using alimiter-discriminator detector for reasonable performance at weak RFsignal levels. However, the channel bandwidth constraints limit themaximum data “high” data rate that can be utilized for transmitting NRZcoded data. Significant improvements in system throughput potential canbe realized within the allotted bandwidth by extending the concept ofadaptively selecting data rate to include switching between sourceencoding methods. The preferred approach is to continue to use NRZcoding for the lower system data rate and substitute partial response(PR) encoding for the higher rate. The throughput improvements of aNRZ/PR scheme over an NRZ/NRZ implementation are obtained at the expenseof additional complexity in the baseband processing circuitry. Anexample of a transceiver using such an approach can be found in thepreviously incorporated patent application of Ronald L. Mahany, U.S.Ser. No. 07/485,313, filed Feb. 26, 1990.

Partial response encoding methods are line coding techniques which allowa potential doubling of the data rate over NRZ encoding using the samebaseband bandwidth. Examples of PR encoding methods include duobinaryand modified duobinary encoding. Bandwidth efficiency is improved byconverting binary data into three level, or pseudo-ternary signals.Because the receiver decision circuitry must distinguish between threeinstead of two levels, there is a signal to noise (range) penalty forusing PR encoding. In an adaptive baud rate switching system, theeffects of this degradation are eliminated by appropriate selection ofthe baud rate switching threshold.

Since PR encoding offers a doubling of the data rate of NRZ encoded datain the same bandwidth, one possible implementation of a NRZ/PR baud rateswitching system would be a 4800/9600 bit/sec system in which thelow-pass filter bandwidth is not switched. This might be desirable forexample if complex low-pass filters constructed of discrete componentshad to be used. Use of a single filter could reduce circuit costs andprinted circuit board area requirements. This approach might also bedesirable if the channel bandwidth were reduced below what is currentlyavailable.

The preferred implementation with the bandwidth available is to use PRencoding to increase the high data rate well beyond the 9600 bit/secimplementation previously described. An approach using 4800 bit/sec NRZencoded data for the low rate thereby providing high reliability andbackward compatibility with existing products, and 16K bit/sec PRencoded transmission for the high rate may be utilized. The PR encodingtechnique is a hybrid form similar to duobinary and several of itsvariants which has been devised to aid decoding, minimize the increasein hardware complexity, and provide similar performance characteristicsto that of the previously described 4800/9600 bit/sec implementation.While PR encoding could potentially provide a high data rate of up to20K bit/sec in the available channel bandwidth, 16K bit/sec ispreferable because of the practical constraints imposed by oscillatortemperature stability and the distortion characteristics of IF bandpassfilters.

EXCHANGING PARAMETERS

All of the above referenced parameters must be maintained in localmemory at both the transmitter and the receiver so that successfulcommunication can occur. To change the communication environment bychanging an operating parameter requires both synchronization betweenthe transceivers and a method for recovering in case synchronizationfails.

In a preferred embodiment, if a transceiver receiving a transmission(hereinafter referred to as the “destination”) determines that anoperating parameter needs to be changed, it must transmit a request forchange to the transceiver sending the transmission (hereinafter the“source”). If received, the source may send an first acknowledge to thedestination based on the current operating parameter. Thereafter, thesource modifies its currently stored operating parameter, stores themodification, and awaits a transmission from the destination based onthe newly stored operating parameter. The source may also send a “noacknowledge” message, rejecting the requested modification.

If the first acknowledge message is received, the destination modifiesits currently stored operating parameter, stores the modification, sendsa verification message based on the newly stored operating parameter,and awaits a second acknowledge message from the source. If thedestination does not receive the first acknowledge, the destinationsends the request again. If after several attempts the first acknowledgeis not received, the destination modifies the currently storedparameter, stores the modification as the new operating parameter, and,based on the new parameter, transmits a request for acknowledge. If thesource has already made the operating parameter modification (i.e., thedestination did not properly receive the first acknowledge message), thedestination receives the request based on the new parameters andresponds with a second acknowledge. After the second acknowledge isreceived, communication between the source and destination based on thenewly stored operating parameter begins.

If the destination does not receive either the first or the secondacknowledge messages from the source after repeated requests, thedestination replaces the current operating parameter with a factorypreset system-default (which is also loaded upon power-up). Thereafter,using the system-default, the destination transmits repeated requestsfor acknowledge until receiving a response from the source. Thesystem-default parameters preferably define the most robustconfiguration for communication.

If after a time-out period the second request for acknowledge based onthe newly stored operating parameters is not received, the sourcerestores the previously modified operating parameters and listens to arequest for acknowledge. If after a further time-cut period a requestfor acknowledge is not received, the source replaces the currentoperating parameter with the factory preset system-default (which is thesame as that stored in the destination, and which is also loaded uponpower-up). Thereafter, using the common system-default, the sourcelistens for an acknowledge request from the destination. Once received,communication is re-established.

Other synchronization and recovery methods are also contemplated. Forexample, instead of acknowledge requests originating solely from thedestination, the source might also participate in such requests.Similarly, although polling is the preferred protocol for carrying outthe communication exchanges described above, carrier-sensemultiple-access (CSMA) or busy tone protocols might also be used.

In addition, Appendix F provides a list of the program modules which arefound in Appendix G. These modules comprise another exemplary computerprogram listing of the source code (“C” programming language) used bythe network controllers and intelligent base transceivers of the presentinvention. Note that the term “AMX” found in Appendices F and G refersto the operating system software used. “AMX” is a multitasking operatingsystem from KADAK Products, Ltd., Vancouver, B.C., Canada.

As is evident from the description that is provided above, theimplementation of the present invention can vary greatly depending uponthe desired goal of the user. However, the scope of the presentinvention is intended to cover all variations and substitutions whichare and which may become apparent from the illustrative embodiment ofthe present invention that is provided above, and the scope of theinvention should be extended to the claimed invention and itsequivalents. It is to be understood that many variations andmodifications may be effected without departing from the scope of thepresent disclosure.

1-47. (canceled)
 48. A communications network for collecting data,segmenting the data and communicating the data segments, comprising: afirst transceiver; a second transceiver; said first transceiveridentifying the occurrences of failed transmissions from said firsttransceiver to said second transceiver, and, based on an evaluation ofsuch occurrences, said first transceiver adjusts the size of datasegments to be transmitted.
 49. The network of claim 48, wherein thedata segments are sized in proportion to a failure rate.
 50. The networkof claim 48, wherein a default data segment size is based on acorrelation distance.
 51. The network of claim 48, wherein a defaultdata segment size is a largest normal segment size.
 52. The network ofclaim 48, wherein the data segment size is reduced until a number offailed transmissions is reduced to an acceptable level.
 53. The networkof claim 48, wherein the data segment size is reduced in response to areceived signal strength indicator transmitted to the first transceiver.54. The network of claim 48, wherein the data segment size is adjustedbased on a weighted average of failed transmissions.
 55. The network ofclaim 48, wherein said second transceiver indicates a failed datasegment transmission by sending a “not acknowledged” signal to saidfirst transceiver.
 56. The network of claim 48, wherein said secondtransceiver indicates a failed data segment transmission by not sendingan “acknowledged” signal to said first transceiver.
 57. A method for useby a first controller in a wireless communications network, said methodcomprising: transmitting data segments to a second controller;determining at least one occurrence of a failed transmission from saidfirst controller to said second controller; and adjusting, after saiddetermining said at least one occurrence of a failed transmission, thesize of data segments to be transmitted.
 58. The method of claim 57,comprising determining an occurrence of a failed transmission based onthe failure of said second controller to acknowledge said transmission.59. The method of claim 57, comprising determining an occurrence of afailed transmission based on receipt of a not acknowledged signal fromsaid second controller.
 60. The method of claim 57, wherein the datasegment size is adjusted based on a weighted average of a number offailed transmissions.
 61. The method of claim 57, wherein the datasegment size is adjusted based on a received signal strength indicatedby said second controller.
 62. The method of claim 57, wherein the datasegment size is reduced until failed transmissions are reduced to anacceptable level.
 63. The method of claim 57, wherein a normal datasegment size is based on a correlation distance.
 64. The method of claim57, wherein the data segments are sized in inverse proportion to anaverage rate of failed transmissions.
 65. The method of claim 57,wherein adjusting the size of data segments to be transmitted to saidsecond controller is based on a number of failed transmissions from saidfirst controller to said second controller.
 66. The method of claim 57,wherein said first controller and said second controller each comprise atransceiver.
 67. A method of communicating between a first controllerand a second controller over a wireless medium, said method comprising:sending, by said first controller, a data transmission to said secondcontroller where said data transmission has a predetermined segmentsize; determining, by said first controller, whether there was a failureby said second controller to receive at least one segment; reducing, bysaid first controller, the segment size of said data transmission basedon a determination of a failure of said second controller to receive atleast one segment; and resending, by said first controller, said datatransmission to said second controller using said reduced segment size.68. The method of claim 67, wherein said first controller determinesthat there was failure to receive a segment based on the failure of saidsecond controller to acknowledge the receipt of said segment.
 69. Themethod of claim 67, wherein said first controller determines that therewas a failure to receive a segment based on the receipt from said secondcontroller of a not acknowledged signal.
 70. The method of claim 67,wherein said first controller reduces the segment size based on aweighted average of failed transmissions.
 71. The method of claim 67,wherein said first controller reduces the segment size based on a movingaverage of failed transmissions.
 72. The method of claim 67, whereinsaid first controller sets the segment size based on a correlationdistance.
 73. The method of claim 67, wherein said first controller setsthe segment size inversely proportional to a rate of failedtransmissions.
 74. The method of claim 67, wherein said first controllerreceives a received signal strength indicator from said secondcontroller, and adjusts said segment sized based on said signal strengthindicator.
 75. The method of claim 67, wherein said first controllerreduces said segment size in increments.
 76. The method of claim 67,wherein said first controller and said second controller each comprise atransceiver.
 77. A system, for use in a communications network forcollecting data, segmenting the data and communicating the datasegments, comprising: a first controller, said first controlleridentifying the occurrences of failed transmissions from said firstcontroller to a second controller, and, based on an evaluation of suchoccurrences, said first controller adjusts the size of data segments tobe transmitted.
 78. The system of claim 77, wherein the data segmentsare sized in proportion to a failure rate.
 79. The system of claim 77,wherein a default data segment size is based on a correlation distance.80. The system of claim 77, wherein a default data segment size is alargest normal segment size.
 81. The system of claim 77, wherein thedata segment size is reduced until a number of failed transmissions isreduced to an acceptable level.
 82. The system of claim 77, wherein thedata segment size is reduced in response to a received signal strengthindicator transmitted to the first controller.
 83. The system of claim77, wherein the data segment size is adjusted based on a weightedaverage of failed transmissions.
 84. The system of claim 77, wherein afailed data segment transmission is indicated by receipt at said firstcontroller of a “not acknowledged” signal from said second controller.85. The system of claim 77, wherein a failed data segment transmissionis indicated by non-receipt at said first controller of an“acknowledged” signal from said second controller.
 86. The system ofclaim 77, wherein said first controller and said second controller eachcomprise a transceiver.
 87. A system for use in a wirelesscommunications network, said system comprising: a first controller, saidfirst controller transmits data segments to a second controller, saidfirst controller determines at least one occurrence of a failedtransmission to said second controller, and said first controller, afterdetermining said at least one occurrence of a failed transmission,adjusts the size of data segments to be transmitted.
 88. The system ofclaim 87, wherein said first controller determines an occurrence of afailed transmission based on the failure of said second controller toacknowledge said transmission.
 89. The system of claim 87, wherein saidfirst controller determines an occurrence of a failed transmission basedon receipt of a not acknowledged signal from said second controller. 90.The system of claim 87, wherein the data segment size is adjusted basedon a weighted average of a number of failed transmissions.
 91. Thesystem of claim 87, wherein the data segment size is adjusted based on areceived signal strength indicated by said second controller.
 92. Thesystem of claim 87, wherein the data segment size is reduced untilfailed transmissions are reduced to an acceptable level.
 93. The systemof claim 87, wherein a normal data segment size is based on acorrelation distance.
 94. The system of claim 87, wherein the datasegments are sized in inverse proportion to an average rate of failedtransmissions.
 95. The system of claim 87, the size of data segments tobe transmitted is adjusted based on a number of failed transmissionsfrom said first controller to said second controller.
 96. The system ofclaim 87, wherein said first controller and said second controller eachcomprise a transceiver.